Subwoofer Cable Connections and Selection

I'm a little confused about connecting my sub to my pre via line level.   Right now I have a 4 meter cheapo RCA interconnect that I probably got at Best Buy and want to upgrade. My pre has a L&R line out and my sub has a L&R line in.  But all the sub interconnects I see are sold as a single cable.  Everything I am reading online assumes there is a sub out on the pre and then that can go into either the left or right input on the sub.  But I have found nothing on a pre with left and right.  Can I just get a single interconnect and go from the pre left to the sub left and leave the right open on both?  Maybe the two outputs are to feed two subs?

Also, I see many sub interconnects w/ and attached spade connector.  I don't think I can use that.  How would that be used?

Here are a couple products I found that would be in my price range (<$200)
I have a Cambridge Audio 851N and Velodyne 1215X.  


You have two options. You can use a simple y adapter from the preamp and go into the sub inputs,that way the speakers will run full range.
You can go from the sub out back to the amp, if you do that the speakers will be high passed from the sub. If you run the speakers full range you can use this adapter on the preamp. You need two pairs of interconnects to do any of these options. The spade connector is if you want to use the speaker level option.
This manual shows all the options on hooking up a subwoofer!
Thanks yogi.  As I was looking at the back of my sub I scraped the dust off the interconnects and saw they are Starightwire.  Laser Link model is what I have for my other interconnects so these are probably the same.  Better than I thought and now I'm not sure that an upgrade is warranted.  They are standard interconnects so there is a left and right on both ends.

I am still a little confused as to why all the cables for subs are single cables but it looks like two may be required without using a Y adapter.  Is that just to make it cheaper?  So do I get 2 Y connectors, one for the preamp and one for the sub and put a single interconnect between them?  I noticed the Straightwire sub ICs have a built in Y but have not seen that on others (

I would rather not go back from the sub to the amp because I think that's just too much of a run and a chance to degrade the signal.  I'm also bi-wiring so I already have a lot of wire coming out the back of the sub so no need to add more wires via speaker level connection.

Finally, is there a difference between cables made for subs and a standard interconnect like I have?  With all things being equall, will a sub IC sound better than a standard IC when connected to a sub?

Thanks for the links too. 

Ken, You need two Y connectors on the preamp outputs.The left channel will go to the amp left in and sub left in and the right channel amp right in and sub right in. You need a pair of interconnects to do this. The standard pair of IC’s is fine. The single sub IC is used when a AVR is used that has a subwoofer output. If you look at that SVS owners manual page 8,9,10, you will see what I am talking about.
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I decided to stick with my Straighwire interconnects.  I guess I just got confused seeing all the single sub cables and no examples of a 2-channel pre with a L&R out.  I also ocompletely forgot I had decent ICs to begin with. It's all hooked up good.  Thanks to everyone for your input.
Straightwire makes "Y" cables connector subwoofer cables, all one piece.  Single ended RCA at the DVD players Line level output and two RCA's (red/white) at the subwoofer line level input of the sub. I use one on my Oppo to Velodyne.